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Flashcards in biology chapter 7 Deck (69):
1

nervous system

enables organisms to receive and respond to stimuli from their external and internal environments

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neurons

are the functional units of the nervous system

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dendrites

are cytoplasmic extensions that receive information and transmit it toward the cell body

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cell body (soma)

contains the nucleus and controls the metabolic activity of the neuron

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axon

is a long cellular process that transmits impulses away from the cell body

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myelin

insulating substance that cover axons, which allow axons to conduct impulses faster

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oligodendrocytes

produce myelin in the central nervous system

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schwann cells

produce myelin in ther peripheral nervous sytem

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nodes of Ranvier

the gaps between segments of myelin

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synapse

or synaptic cleft, which is the fap between the axon terminals of one cell and the dendrites of the next cell

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action potentials

impulses that travel the length of the axon and invade the nerve terminal, thereby causing the release of neurotransmitter into the synapse

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resting potential

when a neuron is at rest, the potential difference between the extracellular space and the intracellular space

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typical resting membrane potential

is -70 millivolts (mV) which means that the inside of the neuron is more negative than the outside

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minimum threshold membrane potential

(usually around -50 mV) is the level at which an action potential is initiated

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repolarization

returns the cell to a more negative potential

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refractory period

immediately following an action potential, it may be very difficult or impossible to initiate another action potential

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synapse

the gap between the axon terminal of one neuron and the dendrites of another neuron

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neurotransmitters

the nerve terminal contains thousands of membrane bound vesicles full of chemical messengers

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curare

blocks the post synaptic acetylcholine receptors so that acetylcholine is unable to interact with the receptor. This leads to paralysis by blocking nerve impulses to muscles

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botulism toxin

prevents the release of acetylcholine from the presynaptic membrane and also results in paralysis

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anti-cholinesterases

are used as nerve gases and in the insecticide Parathion. As the name implies, these substances inhibit the activity of the acetylcholinesterase enzyme. As a result the acetylcholine is not degraded in the synapse and continues to affect the post-synaptic membrane. therefore, no coordinated muscular contractions can take place

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afferent neurons

neurons that carry sensory information about the external or internal environment to the brain or spinal cord

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efferent neurons

neurons that carry motor commands from the brain or spinal cord to various parts of the body

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plexus

a network of nerve fibers

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ganglia

clusters of neuronal cell bodies

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central nervous system

consists of the brain and spinal cord

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brain

the brain is a mass of neurons that resides in the skull. Its functions include interpreting sensory information, forming motor plans, and cognitive function (thinking). The brain consists of an outer portion called the gray matter (cell bodies) and an inner white matter (myelinated axons). the brain can be divided into the forebrain, midbrain, and hindbrain)

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forebrain (prosencephalon)

the forebrain consists of the telencephalon and the diencephalon

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cerebral cortex

which is the highly convoluted gray matter that can be seen on the surface of the brain

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olfactory bulb

is the center for reception and integration of olfactory input

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diencephalon

contains the thalamus and hypothalamus

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thalamus

is a relay and integration center for the spinal cord and cerebral cortex

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hypothalamus

controls visceral functions such as hunger, thirst, sex drive, water balance, blood pressure, and temperature regulation

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midbrain

is a relay center for visual and auditory impulses. It also plays an important role in motor control

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hindbrain

is the posterior part of the brain and consists of the cerebellum, the pons and the medulla

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cerebellum

helps to modulate motor impulses initiated by the cerebral cortex, and is important in the maintenance of balance, hand-eye coordination, and the timing of rapid movements

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pons

is to act as a relay center to allow the cortex to communicate with the cerebellum

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medulla

controls many vital functions such as breathing, heart rate, and gastrointestinal activity

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brainstem

constituted by the midbrain, pons, and medulla

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spinal cord

is an elongated extension of the brain which acts as the conduit for sensory information to the brain and motor information from the brain

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peripheral nervous system

consists of nerves and ganglia

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somatic nervous system

innervates skeletal muscles and is responsible for voluntary movement

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autonomic nervous system

also called the involuntary nervous system because it regulates the body's internal environment without the aid of conscious control

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sympathetic nervous system

is responsible for the "flight or fight" responses that ready the body for action in an emergency situation. It increases blood pressure and heart rate, it increases blood flow to skeletal muscles and it decreases gut motility. It also dilates the bronchioles to increase gas exchange. it uses norepinephrine as its primary neurotransmitter

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parasympathetic nervous system

acts to conserve energy and restore the body to resting activity levels following exertion ("rest and digest"). It acts to lower heart rate and to increase gut motility. It uses acetylcholine as its primary neurotransmitter

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the eye

detects light energy (as photons) and transmits information about intensity, color, and shape to the brain

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sclera

thick, opaque layer that covers the eyeball. It is also known as the white of the eye

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choroid layer

which helps to suppy the retina with blood. It is a dark, pigmented area that reduces reflection in the eye

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retina

innermost layer of the eye, which contains the photoreceptors that sense light

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cornea

transparent at the front of the eye, bends and focuses light rays

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iris

responds to the intensity of light in the surroundings

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lens

suspended behind the pupil and focuses the image onto the retina

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photoreceptors

that transduce light into action potentials

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cones

respond to high intensity illumination and are sensitive to color

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rods

detect low intensity illumination and are important in night vision

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rhodopsin

absorbs a single wavelength

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blind spot

the point at which the optic nerve exits the eye because photoreceptors are not present there

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aqueous humor

is the thick watery liquid between the lense and cornea formed by the eye and exits through ducts to join the venous blood

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myopia (nearsightedness)

occurs when the image is focused in front of the retina

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hyperopia (farsightedness)

occurs when the image is focused behind the retina

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astigmatism

is caused by an irregularly shaped cornea

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cataracts

develop when the lens becomes opaque; light cannot enter the eye and blindness results

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glaucoma

is an increase of pressure in the eye due to the blocking of the outflow of the aqueous humor

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the ear

transduces sound energy (pressure waves) into impulses perceived by the brain as sound

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outer ear

which consists of the auricle (external ear) and the auditory canal

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tympanic membrane

(eardrum) of the middle ear, which vibrates at the same frequency as the incoming sound

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ossicles

(malleus, incus, and stapes) amplify the stimulus, and transmit it through the oval window

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inner ear

consists of the cochlea and the vestibular apparatus

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vestibular apparatus

is involved in maintaining equilibrium